Contact blade mounting for relays having an integral resilient means for biasing said blade in position



Aug. 31, 1965 w. D. MAYNARD 0 7 CONTACT BLADE MOUNTING FOR RELAYS HAVING AN INTEGRAL RESILIENT MEANS FOR BIASING SAID BLADE IN POSITION Original Filed Nov. 28, 1962 2 Sheets-Sheet l FIGI FIG.2

INVENTOR- W.D.MAYNARD HIS ATTORNEY 3,204,072 GRAL Aug. 31, 1965 w. D. MAYNARD CONTACT BLADE MOUNTIN RESILIENT MEANS FOR Original Filed Nov. 28, 1962 G FOR RELAYS HAVING AN INTE BIASING SAID BLADE IN POSITION 2 Sheets-Sheet 2 FIG. 4

INVENTOR. W. D. MAYNARD HIS ATTORNEY United States Patent 3,204,072 CONTACT BLADE MOUNTING FOR RELAYS HAVING AN INTEGRAL RESILIENT MEANS FOR BIASING SAID BLADE IN POSITION Wheeler D. Maynard, Mention, N.Y., assignor to General Signal Corporation, a corporation of New York Original application Nov. 23, 1962, Ser. No. 246,637. Divided and this application Mar. 30, 1965, Ser. No. 444,001

9 Claims. (Cl. 200-166) The present application is a division of my copending application Ser. No. 240,637, filed November 28, 1962,

which parent application is a continuation in part of Ser.

No. 142,391, filed October 2, 1961 and now abandoned.

The present invention relates to the mounting of contact blades in an electromagnetic relay or other similar device, and, more particularly pertains to a contact blade mounting arrangement wherein the blades may be readily mounted in precise alignment and stacked relationships during assembly which relationships become fixed when the various parts are finally secured.

In the construction of relays or like switching device, the contact blades of the relay must be properly aligned with the magnetic structure and with respect to each other. It is proposed to accomplish this by properly aligning a basic portion of the mounting structure with the relay core, and then accurately and precisely mounting insulative waters or contact beds with respect to such basic portion to form a stacking of parts. Each contact bed or wafer contains slots for its contact blades, "and each slot has one side accurately and precisely located with respect to all other corresponding sides of the slots. The other side of each slot has a resilient means for pressing its respective contact blade into position against the aligned side of the slot. Each slot also contains a key for determining the longitudinal position of its blade. In addition, each blade has tines or sharp projections which bite into its wafer or bed when the stacking assembly is clamped together and the holding rivets are set.

Thus, one object of this invention is to provide an improved relay assembly wherein the various contact blades can be afiixedly and retainedly positioned in proper and precise alignment in their respective individual insulating mounts with zero tolerance and to remain in such precise position, not only when completely assembled, but when the individual mounts are being handled during assembly.

A further object of the present invention is to provide an economical way in which the assembly of contact blades and wafers may be properly aligned and yet may be permanently held when the final securing operation is performed.

Another object of the invention is to provide a contact blade mounting assembly wherein the insulative wafers and contact blades are each constructed to insure that the contact blades remain in proper longitudinal position both during assembly and when the final assembly of the stacked members is completed.

A still further object of this invention is to proivde an improved relay assembly which permits the relay to be used in various applications and which is made up of components that are either moulded or stamped and require no machining operation.

Other objects, purposes, and characteristic features of this invention will become apparent from the specification, the drawings, and the appended claims.

back end of the relay when taken along line 2-2 in FIG. 1 and viewed in the direction of the arrows;

FIG. 3 is an enlarged isometric view of one contact blade mounting member employed in the relay of FIG. 1 to show its configuration for holding the contact blades in proper aligned position for assembly and illustrating fragmentarily one contact blade in such position.

IG. 4 is a sectional top view of the relay shown in FIG. 1 with certain parts removed to show how the core of the relay is configurated to fit the other parts of the relay; and

FIG. 5 is a front view of the relay of FIG. 1 with certain parts removed to show the contacts and the operating card attached to the armature as Well as the movable contact springs.

Generally speaking, and without attempting to limit the scope of the present invention, the relay is comprised of an elongate core of rectangular cross-section having a pair of coil structures positioned intermediate the ends thereof. An armature, also of substantially rectangular cross-section, is operably connected to the core by insert ing one end of the armature through an enlarged portion of an irregularly shaped opening provided adjacent one end of the core. The armature is retained in such position by a pair of mating plastic blocks which are so formed to embrace intimately the upper and lower faces of the core adjacent one end thereof with a portion of one block extending into the irregular opening of the core. One of the mating plastic members and the armature has a portion for retaining a spring to hold resiliently the armature against those edges of the portion of the irregular opening of the core on which it is adapted to pivot during opera tion. This assembly precisely positions the armature without the necessity of adjusting the hinge air gap.

A plurality of molded plastic insulating members or wafers are so configurated to be stacked in intimate relationship on the upper and lower faces of the pair of mated blocks with each insulating member holding in precise alignment a plurality of elongate metallic contact blades. Thus when the fixed end of the relay is completely assembled, the elongate metallic contact blades extend longitudinally of the core in spaced relation from both the upper and lower faces thereof.

Each of the plastic insulating members has a plurality of shallow recesses or grooves for receiving the fixed ends of the contact blades. Each contact bladeis held in precise alignment in is respective slot or recess by a resilient member integral with the insulating wafer for assembly. In use the alignment is maintained against external forces such as handling and curve strain by sharp projections or chisel points which embed into the contiguous surface of the wafer.

The stacked insulating members and the mated blocks are fastened permanently to the core in assembled position by a set of elongate studs which extend through aligned holes in each individual member and which are riveted at one end. Once the rivets are set, the assembly of the fixed end, or rear portion of the relay is completed.

The working end or forward portion of the relay is comprised of an integrally formed molded frame having generally rectangular external configuration similar to that of the stacked assembly at the rear end or fixed end of the relay. This frame has a plurality of spaced partitions to form grate-like openings and a single larger central opening which is generally rectangular but has shoulders and raised surfaces on the side walls. The frame is positioned through the central opening adjacent the front end of the core accurately by the shoulders on the sidewall of the opening cooperating with the core. This frame is fastened thereto by the force of an arcuate spring member that is wedged between opposing surfaces a of the core and the walls of the large central opening. When in this position the free ends of the contact blades each extend through one of the grate-like openings of the frame. The released position of the armature is determined by the internal surface of the walls of the larger central opening. A coil spring engages the armature and the opposite wall of the central opening to bias the armature to this released position.

In the illustrated embodiment of the invention there are two clossely spaced horizontal rows of so-called fixed contact blades above the core, and two closely spaced horizontal rows of so-called fixed contact blades below the core. Each contact blade of one row is aligned with a corresponding contact blade of the other row to constitute front and back contacts respectively. Spring means are mounted in the frame to bias each fixed contact blade in engagement with the adjacent surface of the wall of the opening through which the contact blade extends. Extending through an opening interposed between each of the front and back contact blades is a movable contact blade for engaging a front or back contact selectively in response to the operation of the relay.

A plastic card having a plurality of horizontally extending slits, arranged in rows and columns, each of which is positioned to receive a projection of a movable contact blade, is provided with a central rectangular opening for mounting on the free end of the armature. The plastic card has an integrally formed finger that projects resiliently into the central opening and which fits in a hole in the end of the armature when the card is positioned on the armature. The projections of the movable contact blades are locked in position in the slits. The projections on the contact blades are so formed that the card is locked in operative position by shifting it slightly to one side. The plastic card fixes the position of the movable contact blades relative to the armature so that when the armature is in its released position the contact elements on the movable contact blades engage contact elements on the back contact blades to cause each of them to be lifted slightly from the wall or edge of its opening against the force of the spring means positioned in the frame. When the armature is picked up, the movable contact arms disengage the back contacts to permit them to engage the wall of their respective openings through the pressure of the springs, and the contact elements on th movable contact blades engage and lift the front contact blades from the wall or edge of its opening against the force of the spring means.

In accordance with the present invention, the individual spring means in the frame are so constituted that they are deflected sufliciently when positioned in the openings to provide the proper contact pressure when the movable contact blades are in engagement with the front or back contacts depending upon the position of the armature. This pressure, which is termed armature loading pressure is further able to be more accurate and provide greater stability to the so-called fixed contact blades because of the position of each of the spring means relative to each other and their position of alignment with the air gap of the relay close to the working ends of the contact blades. Thus, the contact blades are merely hinges and the flexibility factor inherent in the contact blades themselves is reduced to an absolute minimum.

The spring means also are so formed that they have relatively low spring constants, that is, constants of proportionality which relate the force exerted by the springs to the amount of spring deflection. Because the amount of spring deflection, during relay operation, is small com pared to the amount the springs are deflected when in assembled position, the exerted spring pressure varies minimally during relay operation from the values preset when inserted. This prolongs the life of the relay, because a wearing of the contact elements on the blades after continued operation does not appreciably affect the contact and armature loading pressure. These desired armature loading and contact pressures are accurately determined by the cooperation of the springs in their compressed condition with the inner faces of the plastic molded structure between which they are compressed.

The residual air gap of the relay, that is, that which exists when the relay armature is in its energized or picked up position is accurately determined by covering that portion of the surface of the armature that is in registry with the magnetic air gap with a thin accurately dimensioned layer of nonmagnetic material. This eliminates necessity for adjusting this air gap by means of pins or the like.

Referring in detail to FIGS. 1, 2 and 3 by numeral of reference, the relay is comprised of a core 10, which may be stamped out from appropriate flat stock. The stamped core 19 is an elongate metallic bar substantially rectangular in configuration and cross section, which has an irregularly configurated opening adjacent its right-hand end and a U-shaped recess at its left-hand end (not shown in drawings). Centrally disposed on the core 10 are a pair of spools 14 which have a generally rectangular central opening for slidably receiving the core 10. An energizing coil 15 is wound on each of the spools 14. An elongate armature that is generally referred to at 16, is substantially rectangular in cross-section and is bent to have a substantially L-shaped configuration, with its short leg 17 at the right-hand end, as viewed in FIG. 1, and its longer leg having an off-set portion 18 at the left-hand end thereof. The armature 16 may be stamped out and formed simultaneously with a progressive die. The righthand leg 17 of the armature 16 has a pair of inwardly extending notches or recesses at opposite side edges, which notches are slightly wider than the thickness of the core 10. In assembling the armature 16 in operative position, the short leg 17 is inserted through the irregular opening in the core at its enlarged portion which is defined by side wall portions 20 (FIG. 4) and then shifted to the left as viewed in'FIGS. 1 and 4 so that the shoulders of the core 10 engage in the notches of the armature leg 17, and surface portion 22 of the armature leg 17 abut against forward wall 23 of the core opening 11 which wall and side edge extends transverse of the axis of the core 10.

With the wound spools 14 and the armature 16 so positioned on the core 10, a molded block 24, of insulating material, is positioned on the core 10 in registry with the opening in the core. This molded block 24 and the other insulative members hereinafter mentionel are preferably a plastic having a high melting point and low expansion characteristics, such as a polycarbonate resin, which may be formed by injection molding.

The block 24 has an irregularly shaped integrally formed projection 25, the configuration of which substantially corresponds to the irregular opening in the core. A spring 39 is compressed in a chamber 31, which chamher is formed by a forward wall 32 on the projection 25 of the block 24 and the rear surface of the short leg 17 of the armature 16 so that the axis of the spring 30 is substantially in registry with the uppermost portion of the transverse side wall of the core opening 11. A spring, seat 33 which fits in a square cavity in the armature leg 17 and an appropriate projection (not shown) on the wall 32 retains the spring 30 in position. The force of the spring 30 resiliently biases the armature in its proper hinged or pivotal position against the forward edge of the irregularly haped opening in the core 10. This assembly renders unnecessary any adjustment of the hinge air gap.

A square headed mounting bolt 34 is positioned with its head in a recess 35, the forward wall of which is rear face 32' of the projection 25 of the molded block 24 so that its shank extends rearwardly through the rear narrow channel of the irregular opening 11 of the core It}. A sleeve 36 may be inserted in the cavity 35 to better secure the bolt 34 against movement and rotation.

Another molded block 38 of insulating material which is of similar overall length and width to the plastic block 24 is positioned against the under plane surface of the core as viewed in the drawings (see FIG. 1). This block 38 has a shallow recess similar to the cross-sectional configuration of the projection 25 of the block 24 and tubular projections similar to those referred to for block 24 so that when the block 38 is pressed against the under surface of the core 10, it mates with the block 24. The upper surface of the block 24 and the lower surface of the block 38 are provided with irregularly shaped shallow recesses into which correspondingly configurated terminal plates 42 and terminal plates 43 seat. Each of the terminal plates 42 and 43, which may be stamped from sheet copper has a laterally projecting ear 44 to which a connector 45 of the windings is attached. Each of the terminal plates 42 and 43 also has a rearwardly extending projection 46 for connection to an external source of energy for energizing the windings 15. Thus, the terminals for energizing each of the windings 14 includes a terminal plate 42 and a terminal plate 43.

A plurality of plastic members or Wafers 50, which are rectangular in configuration and of such a dimension as to be con-extensive with the perimetral surfaces of the molded blocks 24 and 38, when assembled, are positioned in stacked relationship on the upper and lower surfaces of the blocks 24 and 38 respectively. Each of the plastic members or wafers 50, between which contact blades such as 54 and 60 are positioned as hereinafter described, have tubular projections which fit into counterbored recesses of adjoining wafers or beds 50 when stacked in proper position. Nested and stacked against the outer-most insulator wafers or beds 50 are insulator wafers or beds 52, each of which has tubular projections for nesting in the counter-bored tubular projections of its adjacent bed 50. The members 52 have a rectangular recess in one face for receiving a rectangular plate 53. A set of elongate rivets 49 are inserted through suitable openings in the plate 53 and the elongate cylindrical bores formed by the counter-bored tubular projections of the members 52, beds 50, and plastic blocks 24 and 38 to clamp the assembly together, and thus complete the assembly of the fixed end of the relay. The spring plate 53 accommodates thermal expansion and contraction while maintaining tightness of the assembly.

Each of the molded plastic beds 50 is configurated to retain a plurality of the elongate metallic contact blades 54 or 60 which are stamped from flat sheet stock of suitable thickness and after conventional contact elements such as 59 are fastened thereto, they are ready for assembly without the necessity of forming or pretensioning. In the illustrated embodiment of the invention (see FIG. 2), each of the wafers or beds 50 has shallow recesses or slots for holding three of the contact blades, such as 54 or 66. Each of the slots has a side wall 55 against which the contact blades 54 or 60 engage when in the proper precise alignment. An integral projection 56, extending into the slot from each of the side walls 55, fits in a notch in the edge of each of the contact blades 54 to insure that the contact blades are in their proper longitudinal position. The side Wall op- Iposite to side wall 55 of each of the slots is provided with an integrally formed finger 57 which normally extends resiliently into the slot, but when a contact blade such as 54 is positioned therein, the finger or projection 57 is urged out of the slot to engage against the edge of the contact blade 54-. The force of the finger 57 not only holds the contact blades in intimate engagement with its respective wall 55 for proper precise alignment, but also prevents the inserted contact blade from dropping out of its respective slot or recess while the various plates 50 are being stacked on top of one another and on the blocks 24 and 38 during assembly. By present manufacturing techniques, these critical surfaces 55 of the insulating members 50 can be made parallel to each other 'with a high degree of accuracy, and, by means of the 6 resilient fingers 57, the various contact blades are easily assembled in precise parallel alignment with zero tolerance.

Each of the contact blades 54 and are provided with minute projections 59 which are formed during stamping and embed in the respective recesses of the wafers 50 so that when the fixed end of the relay is assembled, the blades 54 and 60 are fixed in precise alignment against external forces.

It will be noted that the working or left-hand end of the contact blades 60, as viewed in FIG. 1, each have a longitudinally extending fiat finger or projection 61 (FIG. 1) which has a laterally extending hook portion; and during assembly an insulating bed 50 carrying the contact blades 60 is interposed between those carrying the contact blades 54.

The working or front end of the relay assembly includes a molded member 63, which may be made of the same insulating material, as the fixed end of the relay. The member 63 is substantially a rectangular frame that is open at the front and back and has integral partitions arranged to form a grate like structure. The frame 63 has a generally rectangular central opening 64, the upper wall of which is comprised of an integral partition 65 and the lower wall of which is comprised of an integral partition 66. Parallel to and spaced between the top perimetral wall of the member 63 and the integral partition 65 are a pair of narrow parallel partitions or cross members 68 and 659. Also, parallel to and spaced between a partition 70 and the bottom perimetral wall of the member 63 are a pair of spaced narrow parallel partitions or cross members 71 and 72. Vertically extending spaced integral partitions connect partitions 65 and 70 to the top and bottom of the member 63 respectively and to the narrow partitions 68, 69, 71 and 72 to complete the grate-like structure so as to provide a plurality of rectangular openings both above and below the core 19, through which the contact blades extend. These vertical partitions provide strength and rigidity to the member 63. The free ends of the contact blades 54 and 60 are guided into respective openings such as formed by the narrow 'cross members 68 and 69, and the cross members 71 and 72. Suitable ridges in cross member 66 of frame 63 are accurately molded so that their upper surface when engaged by the bottom surface of the core 19 precisely position the core 10 relative to the member 63. To fasten the member 63 to the core 10, an arcuate spring '76 is forced into the rectangular opening 64 in the space between the upper surface of the core 10 and the partition 65.

The offset portion 18 of the armature 16 engages upper surface of the partition 66 to register accurately the dropped away or released position of the relay armature 16.

Referring to FIG. 1, a low rate coil spring 82 is compressed, during assembly, between a spring seat 83 on surface 84 of the partition 65 of the molded member 63 and a spring seat 85 mounted in an opening in the offset portion of the relay armature 16. This spring 82 is provided for continually biasing the armature 16 toward its released position wherein its underside rests firmly on the upper surface of partition 66 of the molded member 63h When the molded member 63 is positioned on the core 10 as described, the working ends of the front contact blades 54 are positioned in the respective openings between the top of the member 63 and the narrow partition 66, and also are positioned in the openings below the core 10 between the partition 70 and the partition 71. The

back contact blades 54 are positioned in the openings between the narrow partition 69 and the partition 65 above the core 10, and the partition 72 and the bottom of the member 63, respectively below the core 10. The socalled movable contact blades 60 are positioned between 7 the partitions 68 and 69 and the partitions 71 and 72, respectively.

The upper surfaces of the partitions 68 and 71 respectively are engaged by the front contact blades 54 to accurately register their released or unengaged position. Back contact arms 54 engage the under surface of the partions 69 and 72 when released to accurately register their released positions. To minimize manufacturing variations, the surfaces of the molded block or frame 63 which register the position of the relay parts, such as the core 10, the contact blades 54, and the armature 16 are arranged for the least accumulation of tolerances and to negate the variation in thickness of parts where possible.

In the preferred embodiment illustrated in FIG. 1, coil springs such as 86 and 87 are inserted in the frame 63 to constantly urge front and back contact blades 54 respectively toward their released position. Springs 86 are inserted between each of the front contacts 54 and the top wall of the frame 63 and the partition 70 respectively. Springs 87 are inserted between each of the back contacts 54 and the bottom wall of the frame 63 and the partition 65 respectively. Circular projections or spring seats are formed integral with the inner face of the top and bottom of the frame 63 and the upper and lower surfaces of the partitions 65 and 70 and on the front and back contact blades 54 so that the springs 86 and 87 are secured close to the base of each bifurcated portion of the contact blades 54. The bifurcation is provided to insure reliability of contact. These coil springs S6 and 87 which have low spring constants, are of such a length that they are compressed a considerable distance when inserted in position so that the desired loading pressures are continually being exerted against the blades 54 and 60. Thus the exerted spring pressures remain substantially constant over their entire operating range because the amount of spring deflection, during relay operation, is small compared to the spring deflection when assembled. Therefore, there is no need for relay adjustment after assembly to obtain the desired loading or contact pressures. Also, there is no need for adjustment to maintain the desired loading or contact pressures, if the silver contact elements 59 have become worn because of continued operation.

Referring to FIG. 1, a thin, accurately dimensioned sheet or plate 96 of suitable nonmagnetic material is attached to the upperside of the left-hand end 18 of the relay armature 16 and covers the working air gap of the relay. This plate 6 is provided to prevent the armature 16 from being stuck in its attracted position by any residual magnetism present in the relay magnetic structure, after the relay windings 15 have been deenergized, to release the armature 16. The sheet 96 is retained in position by the spring seat 85 which is rectangular in crosssection and fits through a corresponding rectangular hole in the sheet 96. The plate 96 and the spring seat 85 held by the pressure of the spring 82.

In view of the foregoing description, it will thus be seen that the present invention has provided a contact blade mounting arrangement whereby a plurality of relay contact blades can be mounted by suitable insulating wafers in stacked relationship, with each contact blade extending in precise operating alignment with adjacent contact blades and with respect to the relay magnetic and contact structure; and, whereby the individual contact blades are readily assembled and then firmly held within their respective contact slots throughout handling of the insulator wafers during stacking of the wafers and contact blades. Final fastening of the holding rivets maintains such relationships during subsequent operation of the relay.

Having thus described an improved contact blade mounting arrangement for relays or the like, it is to be understood at this time that various modifications, adaptations, and alterations may be applied to the specific form shown in the drawings, in order to meet the require- 0 ments of practice, without in any manner departing from the spirit or scope of the present invention.

What I claim is: 1. In a relay including a plurality of elongate contact blades,

(a) an insulating assembly for fastening the plurality of elongate contact blades in precise position insulatively spaced from one another;

(b) said assembly comprising a plurality of molded wafers of insulating material each having integral portions that mate when stacked atop one another in proper assemblage;

(c) each said wafer comprising a plurality of integrally formed grooves in one surface thereof of sufficient width to receive a contact blade;

(d) each said groove having one precisely positioned side wall against which each contact blade is referenced when inserted therein; and

(e) an integral resilient member normally extending into each said groove positioned to engage against a contact blade when inserted in its groove to constantly urge the contact blade against the precisely positioned side wall.

2. A relay as claimed in claim 1 wherein each said resilient member is a tongued projection extending into the groove from the other side wall.

3. In a relay according to claim 1 wherein each of said wafers has a corresponding projection on its surface opposite the groove surface for fitting into the groove of an adjacent wafer when assembled.

4. In a relay as claimed in claim I wherein each groove of a wafer is of sutficient depth to receive the corresponding projection of the adjacent wafer when the contact blade is inserted in the groove and the resililent member is held out of the groove by engagement with the contact blade.

5. In a relay as claimed in claim 1 wherein said insulating assembly includes means positioned to secure said wafers tightly in stacked relationship, and each contact blade has a plurality of integral projections positioned to embed in a contiguous surface of the respective grooves when the wafers are assembled by said securing means.

6. In a relay according to claim It including rivet means extending through the stacked Wafers of the assembly to hold the wafers in assembled relation, and flat spring means interposed in compression between the rivet means at one end thereof and the assembly.

7. In a switching device having a plurality of contact fingers certain of which are movable for engaging adjacent contact fingers during operation of the switching device,

(a) mating insulator members for mounting said con tact fingers in spaced stacked relationship during assembly,

(b) each of said members having at least one contact slot therein to receive one end of a contact finger,

(c) said contact slot being formed with at least one side thereof accurately in registry to be parallel to a corresponding side of the slot of an adjacent mating insulator member, and

(d) a resilient integral projection on said insulator mem ber normally projecting into said contact slot for biasing a contact finger inserted into said contact slot against said one side thereof, whereby each of said contact fingers are held in a predetermined accurate position relative to one another when mounted in said spaced stacked relationship.

8. The combination specified in claim 7 wherein said contact fingers and said contact slots are keyed to fix the lpngitudinal position of said contact fingers in said contact s ots.

9. In a switching device having a plurality of contact blades certain of which are movable for engaging adjacent contact blades when the switching device is operated,

(a) a plurality of insulator members having a configuration of projections and indentations on their sides for precisely and accurately mating each other when located in a stacked relationship,

(b) certain of said insulator members having at least one contact slot therein to receive one end of a contact blade,

(c) said contact slot being formed With at least one side thereof accurately located to be parallel to a corresponding side of a slot of an adjacent insulator member,

(d) said contact slot having a depth corresponding to the normal thickness of its contact blade,

(e) a resilient projection in each said insulator memher having a contact slot normally projecting into its 10 contact slot for biasing its contact blade against said one side thereof,

(15) a plurality of minute sharp projections on each contact finger extending slightly beyond the normal depth of such contact finger,

(g) each contact slot containing means to fix the longitudinal position of its said contact finger, and

(h) means for firmly holding said stacked insulator members together to cause the said sharp projections on said fingers to embed in said insulator members, whereby said contact fingers are held in predetermined accurate positions relative to one another.

No references cited.

15 KATHLEEN H. CLAFFY, Primary Examiner. 

1. IN A RELAY INCLUDING A PLURALITY OF ELONGATE CONTACT BLADES, (A) AN INSULATING ASSEMBLY FOR FASTENING THE PLURALITY OF ELONGATE CONTACT BLADES IN PRECISE POSITION INSULATIVELY SPACED FROM ONE ANOTHER; (B) SAID ASSEMBLY COMPRISING A PLURALITY OF MOLDED WAFERS OF INSULATING MATERIAL EACH HAVING INTEGRAL PORTIONS THAT MATE WHEN STACKED ATOP ONE ANOTHER IN PROPER ASSEMBLAGE; (C) EACH SAID WAFER COMPRISING A PLURALITY OF INTEGRALLY FORMED GROOVES IN ONE SURFACE THEREOF OF SUFFICIENT WIDTH TO RECEIVE A CONTACT BLADE; (D) EACH SAID GROOVE HAVING ONE PRECISELY POSITIONED SIDE WALL AGAINST WHICH EACH CONTACT BLADE IS REFERENCED WHEN INSERTED THEREIN; AND (E) AN INTEGRAL RESILIENT MEMBER NORMALLY EXTENDING INTO EACH SAID GROOVE POSITIONED TO ENGAGE AGAINST A CONTACT BLADE WHEN INSERTED IN ITS GROVE TO CONSTANTLY URGE THE CONTACT BLADE AGAINST THE PRECISELY POSITIONED SIDE WALL. 